Thread feeding buffer

ABSTRACT

A thread feeding buffer for feeding a fiber thread from a magazine roll to a feed apparatus. The thread feeding buffer comprises a thread brake and at least one movable thread guide, on which a thrust force is acting. The moveable thread guide is vertically shiftable and lowered by gravity. The thread runs from a magazine roll, past the brake, through the thread guide and toward a further feed guide in such a way that the thrust force acts for creation of a thread buffer between the brake and the other feed guide, which buffer is variable in length.

FIELD OF THE INVENTION

The present invention is related to a thread feeding buffer for feedinga fibre thread from a magazine roll to a feed apparatus at a robot armwhich is freely movable in the room.

BACKGROUND OF THE INVENTION

The production of fibre reinforced thermosetting plastic products can beautomatized by the use of an industrial robot, by means of which a fibrefeed apparatus can be controlled, so that precise amounts of fibres arefed out which are oriented for maximum strength, without the fibresprojecting out through the outer plastic layer of the product.

Owing to the repeatability of the robot, the quality of these productscan be increased considerably, simultaneously as problems related to badwork environment and labour fatigue can be solved.

The fibre feeding apparatus is preferably located in a feedout headwhich can be mounted upon a movable robot arm. One or more fibre threadsare supplied to the feedout head, which cuts the threads in suitablelengths. The feeding speed of the fibre thread can be in the range ofabout 10 meters per second.

At such a feeding speed, it is difficult to stop the feeding of threadwithout any risk of getting they thread tangled.

THE TECHNICAL PROBLEM

The object of the invention is therefore to provide a thread feedingbuffer which solves the above described problems.

THE SOLUTION

For this object, the invention is characterized by thread brake meansand at least one movable thread guide on which a thrust force is acting,and that the thread is running from the magazine roll, via the brakemeans, through the thread guide and further on towards the feedapparatus in such a way, that the thrust force acts for creation of athread buffer between the brake means and the feed apparatus, whichbuffer is variable in length.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in the following, with reference toan embodiment which is shown schematically on the accompanying drawing,in which

FIG. 1 is a plane view of a thread feeding buffer according to theinvention, and

FIG. 2 shows the thread feeding buffer in FIG. 1 in a side view.

DESCRIPTION OF PREFERRED EMBODIMENTS

The thread feeding buffer according to the drawing comprises a stand 10with two vertical guide rods 11. The stand 10 carries an elbow arm 12with a thread eyelet 13 for a thread 15 which is wound off from a roll14. The thread can consist of a multiple fibre thread of glass, carbonfibre or synthetic fibre. The thread eyelet 13 provides for asubstantially friction free passage of the thread.

The thread runs upwards from the roll 14 which is located at groundlevel, through the thread eyelet 13 and further over a bar 16 whichchanges the direction of pull back vertically down between the guiderods 11. A thread guide 17 is movably guided by the guide rods and isprovided with further thread eyelets 13, through which the thread 15runs. Then the thread runs on from the thread guide 17 in the directionupwards to a thread guide channel 18, which guides the thread further toa not shown robot arm.

A thread brake cooperates with the bar 16 and is composed of a clampplate 19, which is mounted at the outer end of a pneumatic cylinder 20which is connected to the stand 10. The clamp plate can be brought in orout of engagement with the bar 16 by operation of the cylinder 20,whereby the feeding of the thread will be stopped.

The thread feeding buffer operates in the following way: During normalthread feeding, the pulling of the thread, via the thread eyelets 13 andthe bar 16, creates an even resistance in the thread which results in anadvantageous even outfeed. If the robot arm is moving in the room, sothat more or less thread has to be fed out momentarily, the thread guide17 will be able to move up and down respectively along the guide rods,wherein the thread will receive a rapid compensation in length.

If the feeding of the thread is to be stopped, this is made byactivation of pneumatic cylinder 20 which then presses the clamp plate19 against the bar 16. Now the feeding of thread at the end of the robotarm will continue for s short moment while the thread guide 17 movesupwards along the guide rods 11, until the pull in the thread isstopped. When it will be time for restarting the feeding, this will becommenced with a correctly pretensioned thread without the risk of loopsor kinks on the thread.

The invention is not limited to the above described embodiment, butseveral variations are possible within the frame of the accompanyingclaims. For example, the guide rods can be exchanged for other means forcontrolling a buffer of fibre thread. Further, a spring means canreplace the action of gravity upon the thread guide means 17.

I claim:
 1. A thread feeding buffer for a fiber thread fed from a supplyand along a path comprisinga first guide for the thread for receivingthe thread from the supply, a contactable brake surface over which thethread is fed from the first guide; a brake element moveable intocontact with the brake surface for braking movement of the thread pastthe brake surface; a movable thread guide in the path of the thread pastthe brake surface, a support supporting the movable thread guide formovement; a further guide following the movable thread guide in the pathof the thread and past which the thread is drawn; the support enablingthe movable thread guide to be moved by the thread to reduce the lengthof the thread path between the brake surface and the further threadguide upon the brake element engaging the brake surface and alsopermitting the movable thread guide to move to lengthen the distancebetween the brake surface and the further thread guide to absorb slackin the thread on the path between the brake surface and the furtherthread guide.
 2. The thread feeding buffer of claim 1, wherein thesupport supports the movable thread guide for movement in the verticaldirection so that the movable thread guide is normally acted upon bygravity; andthe first guide and the further guide are both locatedvertically above the movable thread guide so that the movable threadguide can move up and down to absorb slack in the thread.
 3. The threadfeeding buffer of claim 1, wherein the brake surface comprises a runnerover which the thread runs and the brake element comprises a pneumaticcylinder and a clamp movable with respect to the cylinder for clampingagainst the brake surface.
 4. The thread feeding buffer of claim 1,wherein the support comprises a generally vertically oriented guide rodon which the thread guide is movable.
 5. The thread feeding buffer ofclaim 1, wherein the first guide and the movable thread guiderespectively comprise eyelets through which the thread passes.
 6. Thethread feeding buffer of claim 1, wherein the first guide and thefurther guide are stationary, relative to the movement of the movablethread guide.